The Piltdown fraud - exposed as a hoax 50 years ago next week - was neither the wickedest scientific fraud ever carried out nor the silliest, but to this day remains the one that everybody has heard about.

Eoanthropus dawsoni, or Piltdown man, was found in a gravel pit at Piltdown in Sussex in 1912 by Charles Dawson, and for 40 years Piltdown man, with his huge, humanlike braincase and apelike jaw, remained on display in what is now the NaturalHistory Museum in London as an example of the notorious "missing link" between humanity and its primate ancestors.

On November 21, 1953, however, scientists pronounced it a crude forgery, the marriage of a modern human skull and an orang-utan's jaw, and decided that the entire package of fossil fragments at Piltdown - which included a ludicrous prehistoric cricket bat - had been planted by someone.

The world of palaeontology went pink, and the conspiracy theorists went ape. There was no shortage of potentially guilty men to name, and for the next five decades, they named them.

The cast of plausible potential pranksters in this anthropological whodunnit includes enthusiastic amateurs, passionate professionals and disinterested jokers.

Theorists have even pointed the finger at a Jesuit priest - Pere Teilhard de Chardin, who posthumously became a New Age guru - and the begetter of Sherlock Holmes himself, Sir Arthur Conan Doyle, who in 1912 composed his own palaeontological thriller, The Lost World.

"Piltdown matters for a number of reasons," says Chris Stringer, head of human origins at the Natural History Museum. "One is that it is still an unsolved mystery: we don't know for sure who did it, how they did it, why they did it. Those mysteries remain. I think we have gone a long way towards building up the true story, but we haven't got the whole story yet."

What is certain is that everything found in the gravel pit was fraudulently placed, and by an expert.

"When you do a dig anywhere, most of the stuff you find is little flakes of bones and you don't know what the hell it is and you can't identify it. In Piltdown, every single fossil was diagnostic of a species and they were all small, so they were all bits that would fit in someone's pocket, or trouser turnup or whatever. So someone had the knowledge to say: how much of a rhino tooth do I need to show it is a rhino?" says Stringer.

There have been several scandals involving planted evidence. Fossil fraud is a lucrative business.

"We get people coming into the museum with supposed Homo erectus skulls they have bought from a trader in Java. They are carved out of fossil elephant bones, and they are beautifully done. People carve them and sell them for $500 [£300], and we have to say: it is a fake, I am sorry."

2. The amazing Tasaday tribe

In 1971 Manuel Elizalde, a Philippine government minister, discovered a small stone age tribe living in utter isolation on the island of Mindanao. These people, the Tasaday, spoke a strange language, gathered wild food, used stone tools, lived in caves, wore leaves for clothes, and settled matters by gentle persuasion. They made love, not war, and became icons of innocence; reminders of a vanished Eden.

They also made the television news headlines, the cover of National Geographic, were the subject of a bestselling book, and were visited by Charles A Lindbergh and Gina Lollobrigida. Anthropologists tried to get a more sustained look, but President Marcos declared a 45,000-acre Tasaday reserve and closed it to all visitors.

After Marcos was deposed in 1986, two journalists got in and found that the Tasaday lived in houses, traded smoked meat with local farmers, wore Levi's T-shirts and spoke a recognisable local dialect. The Tasadays explained that they had only moved into caves, donned leaves and performed for cameras under pressure from Elizalde - who had fled the country in 1983 along with millions from a foundation set up to protect the Tasaday. Elizalde died in 1997.

3. A crop of circles

They appeared overnight in fields in southern England in the 1970s, and spread over the world - and over acres of summer newsprint, too.

Observers talked of balls of light and high-pitched noises over fields of wheat, and experts reached for their favourite "scientific" theories. One group favoured tornado-like vortices in the air, another suggested "directed plasma" while a third argued that ley lines focused a vital geomagnetic current through the Earth.

Intelligent aliens were invoked, along with top secret military experiments and gaseous toxins from below the soil. Some people claimed that the circles revealed mysterious scientific formulae or religious symbols, others that they had healing powers.

Then, in 1991, a pair of crop circle hoaxers confessed and showed the press exactly how they perpetrated their hoaxes. Some buffs were not convinced, however, and still continue to invoke strange forces.

4. The great IQ scandal

Sir Cyril Burt, professor of psychology at University College London, used studies of twins to prove that IQ was mostly inherited. It was the largest study of its kind, so even those who rejected his explanation accepted his figures. He was one of the architects of the much-debated 11+ examination, which determined children's secondary school careers.

After Burt's death in 1971, researchers were shocked to find that some of the key research into IQ was fraudulent.

"The numbers left behind by Professor Burt are simply not worthy of our current scientific attention," said one.

Argument continues about the extent of the fraud, but some people claim he not only invented some of the data but even the names of his research assistants. Even today, the argument over how much of your IQ is down to your genes, and how much down to nurture, remains open.

5. Red faces at Bell Labs

Jan Henrik Schön, a young researcher at Bell Laboratories in New Jersey, had five papers published in Nature and seven in the journal Science between 1998 and 2001, dealing with advanced aspects of electronics. The discoveries were abstruse, but he was seen by his peers as a rising star.

In 2002, a committee found that he had made up his results on at least 16 occasions, publicly embarrassing his colleagues, his employer and the editorial staffs of both the journals that accepted his results.

Schön, who by then was still only 32, said: "I have to admit that I made various mistakes in my scientific work, which I deeply regret." Nature also reported him as adding in a statement, "I truly believe that the reported scientific effects are real, exciting and worth working for." He would say no more.

6. The alien corpse at Roswell

The search for extraterrestrial intelligence is real, though we haven't found them and (probably) they haven't found us. But the fixation with UFOs and alien abductors reached new heights with the television screening of what is claimed to be a film of an autopsy on an alien who died when a flying saucer crashed in 1947 in Roswell, New Mexico.

In 1995, the US Committee for the Scientific Investigation of Claims of the Paranormal challenged almost everything - the age of the film, the photographer's military status, the injuries to the alien and the way close-ups of alien organs went out of focus - about the black and white sequence. "The film has all the earmarks of an obvious hoax," said an investigator.

7. The signature of God

In 1726, Johann Beringer of Würzburg published details of fossils found outside the Bavarian town. These included lizards in their skin, birds with beaks and eyes, spiders with their webs, and frogs copulating.

Other stones bore the Hebrew letters YHVH, for Jehovah, or God. He believed them to be natural products of the "plastic power" of the inorganic world, and said so in a book.

Alas, they had been planted fraudulently by spiteful colleagues. The legend is that Beringer impoverished himself trying to buy back all copies of his book, and the finds became known as lügensteine, or "lying stones".

8. Something for nothing

Cars that run on water, and fusion machines that generate more energy than they use are staples of inventors' fantasy. They pop up all the time. Charles Redheffer raised large sums of money in Philadelphia with a perpetual motion machine and then took it to New York in 1813, where hundreds paid a dollar each to see it.

It did, indeed, seem to keep itself turning. In the end, skeptics removed some wooden strips to find a cat-gut belt drive, which went through a wall to an attic where an old man was turning a crank.

But the dream continues. In 1984, CBS News in the US featured the "energy machine" of Joe Newman, who declared: "Put one in your home and you'll never have to pay another electric bill." People the world over are still getting bills.

9. Soviet spring of Trofim Lysenko

Lysenko was an agricultural researcher who in 1929 claimed to have invented "vernalisation". He chilled and soaked winter wheat, and planted it alongside spring wheat, and reported that he got a better harvest. In fact, vernalisation was an old peasant technique, and Lysenko's experiment was based on one field of wheat, in one season, on his father's farm.

He also claimed that acquired characteristics could be inherited by the next generation - as if parents who go in for weightlifting could be sure of children with big biceps and six-pack abs. This evolutionary heresy is still known as Lysenkoism.

Joseph Stalin liked practical peasants who promised success, and the state bureaucracy wanted immediate improvement in Soviet agriculture - why wait for a five year plan? - so Lysenko came to dominate Soviet biology. His theories were preposterous but he stayed director of the Institute of Agricultural Genetics until February 1965, when an expert committee finally exposed a long career of false data and distorted science.

10. The krypton factor

In 1999, a triumphant team at Lawrence Berkeley National Laboratory in California, bombarded lead with high energy krypton particles and then announced that they had found the superheavy element 116 and, for good measure, element 118 as well.

The US secretary of energy, Bill Richardson, called it "this stunning discovery, which opens the door to further insights into the structure of the atomic nucleus ... "

By 2002, both discoveries had been withdrawn and a physicist, Victor Ninov, had been fired for falsifying data that provided the base for the claims.

"In the end, nature is the checker," said one of the laboratory's directors. "Experiments have to be reproducible."